9 The base of a cuboid has sides of length \(x \mathrm {~cm}\) and \(3 x \mathrm {~cm}\). The volume of the cuboid is \(288 \mathrm {~cm} ^ { 3 }\).
- Show that the total surface area of the cuboid, \(A \mathrm {~cm} ^ { 2 }\), is given by
$$A = 6 x ^ { 2 } + \frac { 768 } { x }$$
- Given that \(x\) can vary, find the stationary value of \(A\) and determine its nature.